Sudoku Boku is a small site for playing and printing sudoku, published by Hamilton Digital Media Limited, a puzzle company registered in England and Wales. Two people work on it, and between them they cover everything you see here.
Who builds it
Brian Hamilton holds an internet engineering degree and has spent thirty years building for the web. On this site that means the generator, the solver, the technique ladder that decides what a difficulty label is worth, and the PDF writer that turns a grid into something a printer can render at any size. The principle he builds to is that a puzzle should state its rules plainly before it asks for anything clever: if you lost a minute working out how to enter a pencil mark, nothing got harder except the interface.
Karan Hamilton designs and tests the puzzles, and looks after nearly everything that isn't code — the game ideas, the instructions, the wording, and the judgement about whether a new board is actually approachable. Her test is that a grid should look inviting before it turns difficult, and that a fair game hands you enough to reason forward with rather than leaving you to guess. A variant is not finished here because it compiles; it is finished when someone meeting it for the first time can start playing without being taught.
The rest of the workshop
The same two people run about ten puzzle sites, a handful of Android apps and a couple of printed puzzle books between them — word searches, solitaire, logic grids and deduction games alongside the sudoku. This site is the corner of that catalogue given over entirely to the nine-by-nine grid and its relatives, which is why it can afford to care about things like whether Evil deserves the name. The rest of the catalogue is listed on the company's own site.
How the puzzles are made
Easy through Expert are generated in your browser. A complete valid grid is built first, then clues are removed one at a time in random order; after each removal the puzzle is re-solved to confirm exactly one solution still exists, and the clue goes back if it doesn't. Nothing is served from a database and nothing is pre-baked.
Each candidate puzzle is then run through a technique solver that works the way a person does — singles, then subsets, then locked candidates, then X-wings and XY-wings — and is labelled by the hardest technique it genuinely requires. Evil and Extreme are drawn from two banks of five thousand grids each, selected because they defeat that ladder outright.
What we don't collect
There are no accounts and no logins. Your current game and your light/dark preference are stored in your own browser and never leave it. Puzzle generation and PDF creation both happen on your device, so the puzzles you solve and the packs you print aren't visible to us.
Getting in touch
If a puzzle looks wrong, a control misbehaves, or something reads badly, please say so via the contact page. Reports about specific puzzles are especially useful — include the difficulty and roughly what you were doing.